Many foods that are consumed today are rich in umami taste. Umami represents the taste of the amino acid L-glutamate and 5′-ribonucleotides such as guanosine 5′-monophosphate (GMP) and 5′-inosine monophosphate (IMP) and is sometimes also called the fifth taste. The word umami derives from the Japanese for delicious and the umami taste can be described as “savoury”, “brothy” or “meaty” taste. The sensation of umami is due to the activation of taste receptor cells assembled into taste buds, distributed across different papillae of the tongue and the palate epithelium (Chandrashekar et al., 2006, Nature, 444, 288-294). Its effect is to balance taste and round out the overall flavor of a dish. Furthermore, umami enhances the palatability of a wide variety of food products. Naturally occurring glutamate can be found for example in many meat and vegetable food preparations (Ghirri et al., 2012, International Journal of Food Sciences and Nutrition, 63(7), 872-881.).
Umami or savoury, meaty taste of a food product can be further achieved and/or enhanced by adding separately monosodium glutamate (MSG) and/or the ribonucleotides GMP and IMP into those culinary recipes. Many taste enhancers comprising such MSG and/or ribonucleotides have been developed by the food industry and are available world-wide in the trade. A wide variety of ready-to-use taste enhancers are therefore available for various different culinary applications and in various different forms such as pastes, powders, liquids, compressed cubes or granules.
The addition of those culinary additives helps to provide deliciousness and enhanced taste appealing properties to food products to which they were added. Indeed, all around the world, deliciousness and appealing taste is perceived as one of the key attributes of a high quality meal. However, in many parts of the world, the addition of MSG and/or ribonucleotides has received bad press and is more and more negatively perceived by consumers. Although MSG and those ribonucleotides are naturally occurring in many food products, such as in tomatoes and meat products, and have been proven to be safe by several organizations including the World Health Organisation (WHO) and the European Food Safety Authority (EFSA), a publication in the New England Journal of Medicine (Kwok, R H M, 1968 New England Journal of Medicine, 278 (14), 796) sparked speculation among consumers about detrimental effects of MSG and ribonucleotides leading many consumers to reject products containing large amounts of such added compounds. There is therefore a strong need for industrial solutions allowing reducing the use of added MSG and ribonucleotides to food or taste enhancing products, without however compromising on umami taste and still ensuring savoury superiority of such culinary products.
For example, in a recent scientific publication from A. Dunkel and T. Hofmann (Dunkel and Hofmann, 2009, J. Agric. Food Chem. 2009, 57, 9867-9877), sensory-directed fractionation of a freshly prepared double-boiled chicken soup led to the identification of the β-alanyl dipeptides, L-anserine, L-carnosine and β-alanylglycine as contributors to the thick-sour and white-meaty orosensation. Quantitative analysis, followed by taste recombination and omission experiments, revealed for the first time that, when present together with L-glutamic acid and sodium and/or potassium ions, sub-threshold concentrations of these three β-alanyl peptides enhance the typical thick-sour orosensation and white-meaty character known for poultry meat. This is a first step in finding new compounds which are able to impart flavour richness and enhance the umami taste effect of MSG, and thereby allowing a reduced use of MSG.
In our co-pending applications EP15153278.5 and EP 15153288.4 we describe how sugar conjugates of dipeptides have a much stronger flavour enhancing effect than their corresponding aglycones. In fact, these sugar conjugates enhance umami perception and induce a thick-sour and white meaty orosensation of a culinary recipe at much lower threshold levels than their corresponding aglycones. Therefore, the sugar-dipeptide conjugates (such as sugar-β-alanyl dipeptide molecules) are more potent flavour and umami taste enhancers than their corresponding aglycones (such as β-alanyl dipeptides). They allow further reducing the amounts and uses of MSG and/or ribonucleotides in culinary food products without compromising flavour richness and/or reducing the typical and well desired umami taste of said products. They also allow generating umami savoury food concentrates which have much less or no MSG and/or ribonucleotides and still provide a strong and typical umami taste if applied to a food product. It even allows generating such umami savoury food concentrates which are much stronger and more concentrated in providing an umami taste to a food product upon application.
Sugar-dipeptide conjugates may be generated in-situ during thermal processing of food raw materials, for example the formation of sugar-β-alanyl dipeptide molecules by condensation of glucose with β-alanyl-dipeptides such as carnosine and anserine. However, the generation of sugar-dipeptide conjugates in such systems are difficult to control and provide low yields. Sugar-dipeptide conjugates may be synthesised, for example in organic solvents, but these solvents are often not suitable for incorporation in food and so the sugar-dipeptide conjugates must undergo expensive purification steps.
There is a need to be able to generate sugar-dipeptide conjugates in high yields and under reproducible conditions. In particular there is a need to be able to generate sugar-dipeptide conjugates using materials and processes which are suitable for the safe production of food ingredients. Ideally all the materials of the reaction mixture are suitable for use in food so the mixture can be incorporated directly. It would be advantageous if the number of different materials in the reaction mixture were minimized, especially materials which are poorly perceived by consumers of food products.
The object of the present invention is to improve the state of the art and to provide an alternative or improved solution to the prior art to overcome at least some of the inconveniences described above. Particularly, the object of the present invention is to provide an alternative or improved solution for making sugar-dipeptide conjugates. The object of the present invention is achieved by the subject matter of the independent claims. The dependent claims further develop the idea of the present invention. Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”.